1. Field of the Invention
The present invention relates to a mold for molding a tire of so-called divided-type mold, where a portion that molds a tread is divided in a plurality of segments and said segments are further provided with a plurality of divided pieces, and to a manufacturing method of a pneumatic tire by which molding is conducted using this mold. In more detail, the present invention relates to shapes of end surfaces in the piece circumferential direction for removing residual air between adjacent pieces of said mold and for inhibiting generation of spew.
2. Description of the Prior Art
In molding a pneumatic tire, a sector divided mold in which a portion that molds a tire tread is divided in a tire circumferential direction has been used. The divided portion is called a segment and generally, a segment is divided into 7 to 13. At the time of molding, each segment moves to the inner side of a radial direction toward a tire rotational axis, the mold is closed, and then, the tire is molded. For example, a mold for molding a tire described in Patent Document 1 (Japanese Laid-Open Patent Publication 2002-361632) is known.
In such a mold, when the mold is closed, the space of even 0.1 mm between segments or pieces allows the rubber to advance in said space, which causes the generation of spew of a tire. For solving this, between adjacent pieces, completely closing at least the space that is inner side of the tire radial direction on an end surface in the circumferential direction (the side of the tire design surface) by a certain pressure thereby preventing the rubber from advancing between pieces can be considered. However, this cannot exhaust remnant air and bubbles are formed in the tire caused by entrained air.
Regarding this issue, the Patent Document 1, (Unexamined Japanese Laid-Open Patent Publication No. 2002-361632) for example, suggests providing space portions that are rubber impermeable and gas permeable between adjacent segments.
The Patent Document 1 exemplifies to form a porous coating film by plasma-spraying metallic materials such as chrome, aluminum, and the like as materials for said space portions.
However, the porous coating film by plasma-spraying as mentioned above is inferior as a material for a segment end surface that is liable to wear for repeated collisions by opening and closure of a mold in addition that it causes rising cost of the mold and therefore, frequent spraying is required for reproducing the mold.
The object of the present invention is to provide a highly durable divided-type mold for molding a tire that can inhibit the generation of spew to a molded pneumatic tire and rubber advancement between pieces and to provide a method for molding the tire.